﻿266 
  Lord 
  Kelvin 
  : 
  

  

  left 
  the 
  system 
  deprived 
  of 
  the 
  further 
  amount 
  of 
  energy 
  

   carried 
  away 
  by 
  ethereal 
  waves 
  into 
  space. 
  

  

  § 
  15. 
  The 
  system 
  in 
  its 
  final 
  state 
  with 
  the 
  electrion 
  at 
  the 
  

   centre 
  of 
  the 
  smaller 
  atom 
  has 
  less 
  potential 
  energy 
  in 
  it 
  than 
  

   it 
  had 
  at 
  the 
  beginning 
  (when 
  the 
  electrion 
  was 
  at 
  the 
  centre 
  

   of 
  A'), 
  by 
  a 
  difference 
  equal 
  to 
  the 
  excess 
  of 
  the 
  work 
  which 
  

   we 
  gained 
  during 
  the 
  approach 
  above 
  that 
  which 
  we 
  spent 
  on 
  

   the 
  final 
  separation 
  of 
  A' 
  and 
  A, 
  plus 
  the 
  amount 
  carried 
  

   away 
  by 
  the 
  ethereal 
  waves. 
  All 
  these 
  items 
  except 
  the 
  

   last 
  are 
  easily 
  calculated 
  from 
  the 
  algebra 
  of 
  the 
  footnote 
  on 
  

   § 
  13 
  ; 
  and 
  thus 
  we 
  find 
  how 
  much 
  is 
  our 
  loss 
  of 
  energy 
  by 
  

   the 
  ethereal 
  waves. 
  

  

  § 
  16. 
  Very 
  interesting 
  statical 
  problems 
  are 
  presented 
  to 
  

   us 
  by 
  consideration 
  of 
  the 
  equilibrium 
  of 
  two 
  or 
  more 
  

   electrions 
  within 
  one 
  atom, 
  whether 
  a 
  polyelectrionic 
  atom 
  

   with 
  its 
  saturating 
  number, 
  or 
  an 
  atom 
  of 
  any 
  electric 
  strength 
  

   with 
  any 
  number 
  of 
  electrions 
  up 
  to 
  the 
  greatest 
  number 
  

   that 
  it 
  can 
  hold. 
  To 
  help 
  to 
  clear 
  our 
  ideas, 
  first 
  remark 
  that 
  

   if 
  the 
  number 
  of 
  electrions 
  is 
  infinite, 
  that 
  is 
  to 
  say 
  if 
  we 
  

   go 
  back 
  to 
  Aepinus' 
  electric 
  fluid, 
  but 
  assume 
  it 
  to 
  permeate 
  

   freely 
  through 
  an 
  atom 
  of 
  any 
  shape 
  whatever 
  and 
  having 
  

   any 
  arbitrarily 
  given 
  distribution 
  of 
  electricity 
  of 
  the 
  opposite 
  

   kind 
  fixed 
  within 
  it, 
  the 
  greatest 
  quantity 
  of 
  fluid 
  which 
  it 
  can 
  

   take 
  is 
  exactly 
  equal 
  to 
  its 
  own, 
  and 
  lodges 
  with 
  density 
  equal 
  

   to 
  its 
  own 
  in 
  every 
  part. 
  Hence 
  if 
  the 
  atom 
  is 
  spherical, 
  and 
  

   of 
  equal 
  electric 
  density 
  throughout 
  as 
  we 
  have 
  supposed 
  it, 
  

   and 
  if 
  its 
  neutralizing 
  quantum 
  of 
  electrions 
  is 
  a 
  very 
  large 
  

   number, 
  their 
  configuration 
  of 
  equilibrium 
  will 
  be 
  an 
  assem- 
  

   blage 
  of 
  more 
  and 
  more 
  nearly 
  uniform 
  density 
  from 
  surface 
  

   to 
  centre, 
  the 
  greater 
  the 
  number. 
  Any 
  Bravais 
  homogeneous 
  

   assemblage 
  whatever 
  would 
  be 
  very 
  nearly 
  in 
  equilibrium 
  if 
  

   all 
  the 
  electrions 
  in 
  a 
  surface-layer 
  of 
  thickness 
  a 
  hundred 
  

   times 
  the 
  shortest 
  distance 
  from 
  electrion 
  to 
  electrion 
  were 
  

   held 
  fixed 
  ; 
  but 
  the 
  equilibrium 
  would 
  be 
  unstable 
  ex- 
  

   cept 
  in 
  certain 
  cases. 
  It 
  may 
  seem 
  probable 
  that 
  it 
  is 
  

   stable 
  if 
  the 
  homogeneous 
  assemblage 
  is 
  of 
  the 
  species 
  which 
  

   I 
  have 
  called* 
  equilateral, 
  being 
  that 
  in 
  which 
  each 
  electrion 
  

   with 
  any 
  two 
  of 
  its 
  twelve 
  next 
  neighbours 
  forms 
  an 
  equi- 
  

   lateral 
  triangle. 
  If 
  now 
  all 
  the 
  electrions 
  in 
  the 
  surface- 
  

   layer 
  are 
  left 
  perfectly 
  free, 
  a 
  slight 
  rearrangement 
  among 
  

   themselves 
  and 
  still 
  slighter 
  among 
  the 
  neighbouring 
  elec- 
  

   trions 
  in 
  the 
  interior 
  will 
  bring 
  the 
  whole 
  multitude 
  (of 
  

   thousands 
  or 
  millions) 
  to 
  equilibrium. 
  The 
  subject 
  is 
  of 
  

  

  * 
  "Molecular 
  Tactics 
  of 
  a 
  Crystal," 
  § 
  4, 
  being 
  the 
  Seconl 
  Robert 
  

   Boyle 
  Lecture, 
  delivered 
  before 
  the 
  Oxford 
  University 
  Junior 
  Scientific 
  

   Club, 
  May 
  16, 
  1893 
  (Clarendon 
  Press, 
  Oxford). 
  

  

  